In high speed printers of the impact type, it is necessary that the record media or paper be maintained in a taut or tensioned condition during the printing operation. As is well known, the paper, in a drum type printer, has a tendency to be moved in the direction of rotation of the drum by reason of the contact of the paper therewith. Likewise, in a band printer, there is a tendency to move the paper in a horizontal direction by reason of the rotation of the band in such direction past the printing station. In the case of a line printer, wherein printing is performed or accomplished a full line at a time, the paper is caused to be incrementally advanced after each and every line of printing. During the time of paper advancement, such paper, although taut and under tension, should be freely movable past the printing station. However, at the time of printing the line, the paper must be held stationary so as to effect a precise line of print upon impact of the hammers against the type characters, whether such characters are on the surface of a rotating drum or on the surface of a moving type band.
Representative prior art in controlling the paper in high speed printers or the like and maintaining the paper in a desired position at the moment of printing include the following patents. U.S. Pat. No. 3,259,288, issued on July 5, 1966 to C. I. Wassermann, shows vacuum tensioning of paper in a high speed printer wherein a chamber has a plurality of port holes provided with adjustable shutters and the vacuum in the chamber is produced by a fan. U.S. Pat. No. 3,550,745, issued on Dec. 29, 1970 to D. Bisone et al., shows a paper arresting device for high speed printers wherein a series of electromagnets are disposed across one side of the paper and cooperating armatures are disposed on the other side for clamping the paper while printing. U.S. Pat. No. 3,568,812, issued on Mar. 9, 1971 to R. J. F. Eitel, discloses a holdback device for controlling the flow of a unit of paper in a high speed line printer wherein a blade or pawl is movably mounted in contact with the paper web and bearing on a fixed surface. The blade or pawl grips the web between it and a drum on the other side of the web. U.S. Pat. No. 3,586,149, issued on June 22, 1971 to R. H. Miller, discloses web tensioning apparatus comprised of a series of elliptical springs mounted on a rotatable rod on one side of the web and a backup bar mounted on a resilient pad adjacent the other side of the web. U.S. Pat. No. 3,799,314, issued on Mar. 26, 1974 to J. E. Smith, shows a platen brake wherein a rod is rotatably mounted adjacent the platen and the form tends to rotate the platen clockwise while the rod, also rotated clockwise by the form, tends to rotate the platen counterclockwise and causes the platen to stop upon stopping the form feed. And, U.S. Pat. No. 3,802,546, issued on Apr. 9, 1974 to C. J. Helms, shows web clamping apparatus comprising a flat coil structure supported by a plurality of flexure members. A permanent magnet is perpendicular to the plane of the coil and a force is produced which acts to move the coil forward to clamp the web against a pressure plate.